Ice bottom blues

According to the latest bulletin from the National Snow and Ice Data Center in the US, Arctic sea ice is likely to be at or about its minimum extent for the summer (as of Sept 17th). The animation above shows how the ice melt proceeded through the summer (up to Sept 14th), and the graph below shows the extent as of Sept 17th — 3.41 million square kilometres (1.32 million square miles).

The NSIDC notes:

The current extent is 760,000 square kilometres (293,000 square miles) below the previous record minimum extent in the satellite record (4.17 million square kilometres or 1.61 million square miles) which occurred on September 18, 2007. This difference is larger than the size of the state of Texas. The ice extent currently tracks nearly 50% below the 1979 to 2000 average minimum extent.

For an insight into what the ice is really like, I recommend Julienne Stroeve’s blog of her trip on the Greenpeace vessel Arctic Sunrise. This is from her most recent entry (Sept 17th):

I have been surprised by the vast expanses of open water that we came upon after entering the ice. The average ice concentration of the last five days has been about 65 percent, with about 36 percent of that ice being first-year ice, 14 percent being multiyear ice and 10 percent being brash ice (small broken ice floes). Air temperatures have been above freezing, even at 82.82N, 15.16E, so that there have been no new ice formation observed the last five days.

Viewers and listeners to the last Climate Show (and my Radio Ecoshock interview before it) will know something of my thinking on what all this portends, but I’ll have a post pulling it all together once the minimum is finally called.

Elsewhere in the Arctic, this year’s Petermann ice island is motoring south down Nares Strait, as this NASA Earth Observatory image shows.

To get an idea just how big this lump of ice is, note that the scale bar in the bottom right of the image is 100 kilometres. It’s big.

Meanwhile, professor Peter Wadhams, head of the Polar Ocean Physics Group at Cambridge, has told the Guardian that he expects the Arctic to be ice-free1 means in summer (Aug/Sept) within four years. Given this summer, I can’t say that I find much to disagree with in his prognosis.

I thought Hansen was appearing in London at a Greenpeace function but it appears the event was held in New York. Supposedly, the event was entitled “The Polar Emergency: Why are rapid changes in the Arctic and Antarctica a matter of global concern?”

It seems that according to HuffPost, there isn’t anything special to note about the Arctic sea ice going into the dumpster other than Hansen et.al.’s usual message, i.e. “we’re running out of time” which may have evolved into “we’re really running out of time” in honor of the melted sea ice.

Hansen thought it worth mentioning that the general public isn’t getting it, a line HuffPost ran with: “there’s a huge gap between what is understood by the scientific community and what is known by the public. Unfortunately that gap is not being closed”.

Hansen, who has predicted that if all fossil fuels are burned it is a “dead certainty” that the planet will become uninhabitable, warned there is too much CO2 in the atmosphere already. Allowing the excess CO2 to stay in the atmosphere for too long, i.e. several centuries say, without eliminating net CO2 emissions and withdrawing some of what’s already been put in, “guarantees disaster”.

But I already knew we were royally screwed, up the proverbial creek without a paddle in a boat that is on fire.

When I heard Greenpeace had Hansen headlining some Arctic ice event of theirs I paid attention for a Hansen assessment of the situation up there. What I was looking for was some statement out of Hansen about what the disappearing sea ice is doing to the planetary energy imbalance.

Hansen has a “Sea Ice Area” page on his website, updated, it says, 2012/09/04, only weeks ago. What he does is plot additional data on a chart that contains the sea ice minimum going back three decades or so. The additional data shows the trend in maximum extent, and the trends in extent at maximum and minimum insolation. Several quotes:

“the figure below suggests that the September 2007 sea ice minimum did not have a correspondingly large effect on the sea ice area at the time of maximum insolation”

“the huge sea ice loss of 2007 caused some scientists and other people to speculate that all Arctic warm-season sea ice may be lost within five years. Sea ice cover is probably not that unstable”

“if Earth’s energy imbalance is restored by decreasing atmospheric CO2 to 350 ppm or less, it may be possible to stabilize or increase the area of Arctic ice”.

I understand why scientists always take the conservative route, but rather than the bog standard 1979-2000 average – yes, I know, climatology – which is, by definition, an average, where was the Arctic ice extent at the starting point in 1979?

Or, can we at least see a series of shorter averages which gives a more realistic picture, if a little scientifically impure. Say 5 year averages over that period?

I guess what I’m asking is if the 30 year average compared to current measurements shows a 50% decrease, what is the decrease from the previous 30 years, which we don’t have, but can we get an idea of it from shorter time frames?

You’ve done very well. And it’s an immensely enjoyable post – gotta love µWatts’ ‘East Antarctic UHI’ as illustrated by this photograph of a temporary Aussie base on the other side of the continent! Still hard to believe he actually wrote it…

I was just testing to see if one of the great unwashed could insert a graphic into a comment and discovered that I cannot. As Gareth’s comments show, being able to use graphics in a comment is a great way to communicate….